This invention relates to a safety device for a hydraulic jack and particularly to an overload alarm device for a hydraulic jack.
It is customary to provide a safety device in most high pressure operating equipment or apparatus. FIG. 1 shows a hydraulic jack which has a safety valve 14 provided on the hydraulic fluid line 13 which connects the cylinders 40 and 16. When the hydraulic pressure in the ram cylinder 16 is extremely high, the valve 15 is closed tightly by the pressure, and the continuously pumped fluid from the cylinder 40 will push against the safety valve 14 which is designed to relieve at a certain pressure and return the fluid to the storage cylinder 11, thereby avoiding the formation of excessive pressure in the ram cylinder 16. Although the safety valve is provided, it cannot make the user aware of the existence of an overload on the hydraulic jack. This is still a deficiency required to be fulfilled.